The present invention relates to a bunching block for use in public utility central offices and more particularly to such a bunching block employed in connection with a McCulloh circuit while being operable at the public utility central office for facilitating location of faults in one or more series interconnected user loops.
McCulloh circuits are widely employed for connection through public utility telephone lines or the like to various subscriber alarm units and associated McCulloh transmitters.
Such circuits are well known and are described for example in U.S. Pat. No. 3,848,241 issued Nov. 12, 1974 and U.S. Pat. No. 3,982,242 issued Sept. 21, 1976. These references are typical of a number of publications disclosing various features and operating characteristics of McCulloh circuits. Accordingly, those references are cited herein as being representative of a relatively large number of disclosures in connecting with McCulloh circuits.
The arrangement and operation of such McCulloh circuits are described briefly below in order to provide a better understanding of the present invention.
Generally, the alarm units may be adapted for a number of applications including fire and/or burglary for example. The alarm units and associated McCulloh transmitters are commonly connected in series and may, for example, include a normally closed switch in series with the line of an individual user loop and a normally open switch connected to ground. The switches are activated by means of a code wheel or the like in a particular sequence commonly responsive to operation of an associated alarm sensor.
When an alarm event occurs, the code wheel rotates and operates the switches, thereby providing a coded set of pulses. Each wheel has different configurations of teeth or cogs to establish a particular set of pulses as a unique code, the pulses being transmitted to a McCulloh receiver which identifies the locations of the alarm from the unique code.
Through this arrangement, large numbers of individual user loops may be connected with a single McCulloh receiver. Commonly, the McCulloh receiver is located at an installation of an alarm company or the like responsible for monitoring the individual user loops and determining if a response is necessary to a coded signal from any of the user loops. In order to assure reliable and continuous service, these monitoring companies typically employ various types of monitoring equipment for determining conditions in the individual user loops. For example, the reference patents cited above each describe different types of test and integrity equipment adapted for use by such a monitoring company to detect various conditions within the individual loops. However, it is again noted that the present invention is concerned with the configuration and operation of bunching blocks provided by a public utility or telephone company for interconnecting the individual user loops with the McCulloh receiver of the monitoring company. Accordingly, equipment of the type referred to immediately above, which is used in conjunction with the McCulloh receiver, is not contemplated as being part of the present invention.
In normal use, relatively large numbers of user loops are interconnected with the McCulloh receiver through lines provided by the telephone company. Because of this arrangement, the telephone company has a separate function of assuring continuity in the connections for the various user loops with the McCulloh receiver. Commonly, relatively large numbers of user loops at a single central office are interconnected in series with each other and with the McCulloh receiver by a bunching block including sets of first and second connectors, the first connectors being coupled with the respective individual user loops, the second connectors providing the series connection with each other and with the McCulloh receiver through external transmission lines. In the past, the first and second sets of connectors have been hard wired together in order to place the individual user loops in series with the McCulloh receiver.
Typically, large numbers of user loops associated with different central offices are first interconnected in series with bunching blocks of the type described above at the individual central offices. The multiple bunching blocks are then also connected in series with each other and with the McCulloh receiver through the external transmission lines.
In any event, whether a single central office or multiple central offices are connected with the McCulloh receiver, it is often necessary for the public utility or telephone company to locate a fault appearing anywhere in a user loop or associated circuitry anywhere along the series connection with the McCulloh receiver.
In the past, it has been common practice to employ a relatively involved manual procedure for isolating such faults. The excessive time and expense in locating faults by these procedures is emphasized by the following summary of steps carried out in the procedure. Furthermore, where bunching blocks multiple central offices are interconnected with each other and with a single McCulloh receiver, it is furthermore necessary to perform the following procedure at each of the central offices or bunching blocks until the fault is located and corrected. The prior art procedure carried out at the bunching block of each central office is as follows:
1. The individual user loops to be tested for possible faults are disconnected from the respective bunching block and from the McCulloh circuit one at a time.
2. The tip and ring connectors employed in the bunching block for connecting the individual user loops in series with the McCulloh circuit are then shorted out in order to individually isolate the respective user loops.
3. A remote test device commonly referred to as a shoe is then installed in place with the tip and ring connectors in the bunching block for the respective user loops to permit testing as described above.
4. After testing with each individual user loop being isolated, hard wiring is again installed between the first and second connectors for the respective user loop.
5. The short is then removed from the tip and ring connector as described above.
6. The above steps are repeated in connection with each individual user loop or with multiple individual user loops if necessary in order to locate the fault. As was also noted above, this entire procedure must be continued if necessary through the bunching blocks in all of the central offices connected in series with the McCulloh receiver until the fault is located.
The time and expense thus required by the telephone company to locate faults in equipment served by the bunching blocks at various central offices is readily apparent from the preceding description.
Accordingly, there has been found to remain a need for an improved method and apparatus for facilitating the rapid location of a fault or faults in the individual user loops connected in series with a McCulloh test circuit.